Acute and chronic airway diseases are among the most common forms of serious illness in the U.S. and worldwide, and much of the morbidity and mortality is caused by mucus obstruction of the ainways. In turn, the mucus obstruction is the result of increased mucus production and subsequent secretion. Despite the medical need, there are no specific and effective therapies to primarily block mucus production. Here we present preliminary data that human chloride channel calcium activated 1 (hCLCAl) provides a critical signal (via primarily MAPK13) to regulate the amount of mucus production. We further hypothesize that increased hCLCAl levels are responsible for excess mucus production in airway disease. We therefore propose that an inhibitor of hCLCAl signaling would be beneficial to treat overproduction of ain/vay mucus and that hCLCAl levels can guide therapy. To further develop our plan for anti-mucus therapy, we propose two aims, the first for target validation with the goal of using hCLCAl level as a clinical biomarker, and the second for assay development with the goal of using hCLCAl signaling as a target for high-throughput screening (HTS). Aim 1 will validate that hCLCAl level and consequent signaling is coupled to mucus production in high- fidelity cell and mouse models and in human subjects. Special approaches include a new library of anti- hCLCAl mAb's, a lead inhibitor of MAPK13, a new aerosol delivery system, and a library of tissue samples from well-characterized asthma and COPD subjects. Aim 2 will optimize and verify assays of hCLCAl signal transduction that can be interrogated with HTS. Special approaches include a human epithelial cell line that is engineered for inducible expression of hCLCAl and consequent MARK activation and mucin gene expression, a newly dedicated HTS system that is fully automated and roboticized for cell-based assay in this cell line and primary-culture ainn/ay epithelial cells, and medicinal chemistry to enable a pilot screen of our initial lead and related compounds. We expect these studies to validate hCLCAl as a new diagnostic and therapeutic target for stratifying and treating patients with overproduction of mucus in ainA/ay diseases. The approach takes advantage of a heretofore unknown mechanism for controlling mucus production. We anticipate developing a high-quality ELISA to monitor hCLCAl levels for guiding patient stratification and therapy and a cell-based assay to screen for hCLCAl inhibitors in an HTS system. The multidisciplinary approach will be facilitated by a team with expertise in all aspects of lung biology and disease as well as drug development. Together, the information from these aims will have a significant impact on diagnosis and therapy of airway diseases by establishing the tools needed for anti-mucus therapy. RELEVANCE (See instructions): Airway diseases ranging from acute respiratory infections to chronic asthma and COPD are among the most common types of serious illness, and much of the morbidity and mortality is due to obstruction of the lung airways by mucus. However, we currently have no specific and effective anti-mucus therapies. This proposal aims directly at this issue by validating a new mechanism to explain overproduction of ainA^ay mucus during disease and by taking the next steps to identify the means to monitor and treat this abnormality.